It depends on the bike for me...
I don't know why, but I love bicycles, always have. I love how they look, sound and feel. I'll admit it - I can be shallow and stupid when it comes to my bicycles. I'll never spend money on clothes, or a car, or a watch, but when it comes to bikes, I like my bling. Some of my bikes are designed with really only practical considerations, but even on those I often find a way to add a touch of bling. It makes no sense, but I like having a campy seat post on my daily commuter. I can't rationally justify spending as much as I did for ti king cages, but I did it. I'm sure it has something to do with saving all my dollars for a mid-range Specialized and being jealous of the guys with their snooty euro bikes when I was 14. I didn't want a car, or fancy sneakers, or a new tv as a teen, I wanted a De Rosa. Now I can afford them (used).